Hi,
I was wondering what is the advantage of having hint bits for OLAP -style workloads, that is when the number of transactions is not that high. If I got it right, in 10 pg_clog pages we can store the status for more than 320000 transactions. That's a lot, in a very small space (80KB?). So I was wondering what's the gain we get from hint bits in cases where pg_clog is "small" (that is, will be cached by postgresql/the OS). does somebody have some numbers on the effect of hint bits on first/second reads? I mean: create mytable as ..... select * from mytable -> this one will update hint bits select * from mytable -> this one will use them to test it I guess we should change the code to have: a version where they are never updated (that is, always look at pg_clog) (so that you don't have to write them the first time, and you'll get the "true" reading time + pg_clog reading time) a version that always set them to COMMITTED (so that you don't have to write them the first time, and you'll get the "true" reading time for the "second" read that would use them, regardless of any pg/OS cache) I'm asking because I don't like having all those writes on the first scan... and I would like to know what the real benefit is for the reads that come after the first one in case there are "few" transactions per second (for example, less than 1 transaction per second) -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
